-We have established a treatment that allows us to efficiently and conditionally immortalize primary human keratinocytes and other epithelial cells by culturing them in the presence of a ROCK inhibitor and with feeder fibroblasts. -The immortalized keratinocytes are invaluable for studies on the long-term persistent HPV DNA replication -Immortalization is conditional -The immortalized keratinocytes are invaluable for studies on gene therapy and gene delivery. -The technique is invaluable for the efficient procurement of cells from individuals with specific genetic and infectious diseases.